Coadsorption　of　carbon　monoxide　(CO)　and　nitric　oxide　(NO)　on　the　Cu　2　O　(111)　surface　was　studied　using　periodic　density　functional　theory　calculations.　It　is　interesting　to　find　that　CO+NO　on　Cu2　O　(111)　could　react　to　form　adsorbed　NCO　surface　species.　Coadsorption　of　CO　and　NO　could　give　rise　to　the　formation　of　a　O-CN-O　complex　well　bound　to　the　Cu2　O　(111)　surface,　in　which　both　the　C-O　and　N-O　bonds　are　greatly　activated　and　the　C-N　bond　is　formed.　Consequently,　the　reaction　of　CO　with　NO　to　form　adsorbed　NCO　and　CNO　species　may　occur,　for　which　it　is　disclosed　that　NCO　formation　is　more　possible　than　CNO　formation　both　thermodynamically　and　kinetically.　In　addition,　our　calculations　of　searching　transition　states　reveal　that　it　is　facile　for　NCO　formation　both　kinetically　and　thermodynamically　when　CO+NO　reaction　takes　place　at　CuCUS　site,　and　is　impossible　when　this　reaction　takes　places　at　Ovac　site.　Moreover,　CO2　species　cannot　form　when　CO+NO　reaction　occurs　at　Ovac　site.　Therefore,　oxygen　vacancy　on　Cu2　O　(111)　does　not　play　a　positive　role　on　CO+NO　reaction　to　forming　NCO,　CNO,　or　CO2　species.　©　2009　American　Institute　of　Physics.